Subterranean drilling systems that employ downhole drilling motors are commonly used for drilling boreholes in the earth for oil and gas exploration. Such subterranean drilling systems typically include a housing enclosing a downhole drilling motor operably connected to an output shaft. One or more thrust-bearing apparatuses may also be operably coupled to the downhole drilling motor for carrying thrust loads generated during drilling operations. A rotary drill bit may also be connected to the output shaft and be configured to engage a subterranean formation and drill a borehole.
Each bearing apparatus may include a stator that does not rotate and a rotor that is attached to the output shaft and rotates with the output shaft. The stator and rotor may each include a plurality of superhard bearing elements or inserts. Each superhard bearing element may be fabricated from a polycrystalline diamond compact (“PDC”) that provides a bearing surface that bears against other bearing surfaces during use.
In a conventional PDC bearing apparatus, a bearing assembly may include a support ring that may be configured to accept a number of superhard bearing elements. The superhard bearing elements may be made from a polycrystalline diamond layer formed on a cemented tungsten carbide substrate.
Despite the availability of a number of different bearing assembly designs, manufacturers and users of bearing apparatuses continue to seek improved bearing apparatus designs and manufacturing techniques.